/Engine/Plugins/Runtime/GeometryCache/Source/GeometryCache/Classes/GeometryCacheTrackStreamable.h
So you can keep the pointer around as long as you know theFGeometryCacheTrackStreamableRenderResourceinstance you got it from stays valid.
[UGeometryCacheTrackStreamable](API\Plugins\GeometryCache\UGeometryCacheTrackStreamable) * GetTrack()